Generally, a desiccant made of silica gel, calcium chloride, etc., is packed in a small bag and is enclosed in a package for use with a dry product. This case, however, has inferior workability in packaging. Besides, the silica gel is a white substance, and, therefore, a moisture absorbing condition in the package cannot be checked from the outside.
To deal with the above problem, a desiccant allowing a check on a moisture absorbing condition, that is, a desiccant with a moisture absorption indicator function, is provided. Such a desiccant is made by mixing silica gel with cobalt chloride, and it thus is blue in a dry condition while it turns pink upon absorbing moisture in the air.
An example of a drying agent with a moisture absorption indicator function is, for example, shown in FIG. 10, which is constructed as a bag-like dehumidifying agent with a humidity indicator. This dehumidifying agent is made by storing a moisture absorbent sheet 1 in a bag 4 made of a nonwoven fabric, and a moisture-absorbing humidity indicator 2 covered with a barrier film 3 is pasted on the moisture absorbent sheet 1. The moisture-absorbing humidity indicator 2 contains cobalt chloride, and the barrier film 3 has micropores. When the moisture absorbent sheet 1 absorbs moisture, the moisture-absorbing humidity indicator 2 absorbs moisture through the micropores of the barrier film 3, thus changing the color of the indicator 2 from blue to pink. When the moisture absorbent sheet 1 dries to be regenerated, the moisture-absorbing humidity indicator 2 then changes its color from pink to blue. Through this color change, the moisture absorption condition of the moisture absorbent sheet 1 can be visually recognized (e.g., see patent document 1).
The conventional example of patent document 1, however, uses cobalt chloride as a moisture absorption indicator substance. When the drying agent with a moisture absorption indicator using such a heavy metal as cobalt is disposed of as trash and is incinerated, the heavy metal is finally discharged into the living environment. This is a situation that people hope to avoid as much as possible to protect the environment. A drying agent having a moisture absorption indicator function but without cobalt, therefore, has been developed.
An example of a package having a moisture absorption function is shown in FIG. 11, which is constructed as a cylindrical moisture-absorbing container. This moisture-absorbing container is made by separately injection molding a screw hollow container (outermost layer) 6 and an inner container (innermost layer) 7 and joining both containers together into an integral form. A cap 8 is screwed and tightened on the hollow container 6 to form a storage container. The inner container 7 is molded out of a resin composition having an indicator function for indicating moisture absorptiveness. This resin composition contains a synthetic zeolite 7a mixed therein, causing the inner container 7 to change its color to clear yellow after moisture absorption, which allows an extent of moisture absorption to be checked (e.g., see patent document 2).
Patent document 1: Japanese Utility Model Application Laid-Open Publication No. 64-28934 (entire description, FIG. 1)
Patent document 2: Japanese Patent Application Laid-Open Publication No. 2004-331855 (entire description, FIG. 1)